Filter



Feb. .23, 1965 L. E. H. REICHSI'EIN FILTER Filed une 21, 1961 f IN VEN TOR.

LANCE ERIC HROLD REKHSTN F l G 2 j on` the" periphery of the drum. i

e, often employed .with the belt, to enhanceits compression United?. States Patent O ce V ,FILTER Lance Eric Harold Reichstein, Toorak, Victoria, Australia,` assigner to Ametek,"lnc., VNew York; N.Y., a

corporation of Delaware 4 f Filed June 21, 1961-, Ser. No. 118,645

2 Claims.. @L1100-162) The present inventionv relates to ,filters ofthe drum type,.and'particularly to a newv` and improved drum type lter embodying cake dewatering mechanism. v Y Y Although the principles of the invention are applicable to various `types of drum filters, they will be shown and described as appliedto a 4drum type :string iilter. t

Filters of the drum typehaving closely spaced, peripherally extending strings that leave andv return to the drumr tangentially are commonly known. The filter cake builds i v up on the courses'fjstring and passes from thedrum as the strings leave the drum surface, thereupon falling into i a collector as the strings. pass `over a breakup roll prior,

4to returning to the drum periphery.

One of the principal'problems of'suchmltersis to reri "Patented Feb. 23,1965

, In one aspect of the invention, arotatable drum iilter may include discharge strings passing over its periphery tangentially passing oli"- the drum, over a discharge roll Y and finally tangentially back onto the drum.` The drum may be partiallyl submerged vWithin a tank containing a slurry to be filtered, and vacuum producing means may be provided .that subjects the submerged peripheralporduce the moisture content of the cakeas much as'possible` prior to the cake being removed' from the drum.Y Q Ithas heretofore beenthe practice to e1nploy"a compressing ctony Y v- Thestring discharge filter does not require airblcl'w back toease .the filter cakeoi the drum atthe point of m'oisturecontent4 because residual filtrate in thezdrainage ,lines is not blown back towardsthe cake by the air blast.

Compression rolls are mechanism which may comprise anV endless -belt that acts` on a substantial portion of the ilter cake that is Vcollected moisture from the filter cakef .Y A y u In still another aspect of the'inventio'n'; cake agitating tion of the drum to a subatmospheric pressure.:l

In another aspect of the invention, aV compression device maycomprise an endlessbelt of canvas or other iiexible material having a width equal to the axial dimen- -V sion of the drum periphery and extending over a periph-` eral arc of the drum between the point where it leaves the slurry andthe point where the strings tangentially leave the d-rum.

In still vanother aspect of the invention, compression rolls,v may ride on the. endless beltfforcing it into. contact with the filter cake, compressing the saineand thereby dewatering the cake. Alternatively, roller means may ,be employed alone without the endless belt for'expressing f means may be provided, and intheembodimentdisclosed it is" shown as avcake `flapper device comprising a rotatable drum having its longitudinalaxis parallel with that Vofthe iilterdrum and located substantially atl the top.

` deadV center thereof. V.:Ii-lexirble iiappers' may be attached i discharge. This sometimes assists Y in` achieving, lovI i In addition, the use of compressionrolls andcompression belt `often assists in two Ways; rst, by sealing incip-` ient cracks in'the filter cake on the drum, thereby pre-v totheiiapperldrum, andas the drum rotates, theseV flappers beat thecake beneath theendless belt, causing fur.-

ther dewatering of thecake, or alternatively, a sheet'of i f liexiblematerial may be maintained in position about "a portion of thedrurn .periphery for receiving the impact e, of the ilappers-wheni thezendlessbelt is' not employed.`

It has been found that vthe combination of these two compressionu'devices` produces .a de'watering of'V the: filter cake farV beyond that Which'each c an effect individually,

j so that the combination is not the'additive eiiect of both V`:-but\ a resulting dewatering of unobvious proportions..

venting channeling ofthe airfthroughthese cracks; and

the formation of thin cakes on thedrum and also promotes Vthe formation of a low den-sity .cake with a higher perdrainage of adhering liquid.

v centage of voids betweentheparticlesto permit easier oflow vacuum in the Vcake forming zoneis often of help in producing low moisture iilter cakes becauseitpromotes The` above, other objects and novel features of the invention Will become apparent from the followingspeciiication and accompanying'drawing whichV is merely exemplary. i

In the drawing: v

FIG. l is an elevational view of a drum filter to which the principles of the invention have been applied; and

FIG. 2 vis a sectional :view taken substantially along line 2 2 of 1216.11. d i, l

i Referring to the drawing, the principles of the inven-` tion are shown as applied to a vacuum drum string iilter including atank` 10 adapted tocontain a` slurry to `be, iiltered. The tank lil may include bearings (not shown)VV :for rotatably, supporting a drum 11 that may be"` driven from a variable speed unit 12 through" gear box 13.

The drum r11 may be of usual construction including a, fabric peripheral co'atingaboutV which aV plurality ofV Y closely spaced stringsv 14 may extend.` VThe strings `14 Wrap around a substantial portion of the periphery of i The principal object of Vthis invention is to provide aVV l drum.- filter embodying compression mechanism `capable of reducing the moisture content of .the iilte'r cake below that heretofore obtained with known compressing devices. d Another object of the invention is-to provide" such `a.

filter in which the, usual compressing Vmechanism isaugmented by a device that decreases the moisture content of the filter cake substantially'belowthat obtainable with the compressing mechanism alone. lStill another object of the invention is .to provide` a drum type filter in'which maximum 'dewatering of the V filter cake is effected'while maintaining a maximum cloth loading v 6o AIVa point 18.

. within the slurry within tank `ltl and may include'V means Y Y for subjecting the submerged peripheral portion thereofV v jected causes the cake to break up and fall into ahopper drum 11, leave it tangentially at a point 15,V pass over a breakup roll 16, thence reversely over an idler roll 17 and finally return tangentially to. theYdrum periphery at The'drum 11 may have a substantial portion submerged to a subatmospheric pressure, thereby causing filter cake to be built up on the drum periphery above the strings 14. As the strings 14leave the drum atpoint 15, the cake which has the strings 14 embeddedV therein is peeled oii theV drum peripheryyand as the `strings pass over the breakup .roll V16, the sharp curve to whichthey are sub- :or the like.

1n order to reduce the moisture content within the cake, compressing means may be employed. In the embodirnent disclosed, this means is shown as supported by a framework including uprights 19 at each end of the tank, and between which the axis of rotation of drum 11 extends.- A curved frame `member 2t)V and cross members 21 and 22 are also provided.

An endless exible belt 23 such asA canvas or the like may wraparound a substantial portionof the periphery of the drum 11 abovefthe slurryfwithin tank 16. It may be guided by an'idle roll y24 mounted on a lever 25 that f is pivotally supported by the cross member 21. Other idle rolls 26, 27 and 28 may be supported by the curved frame member 20. Compressing rolls 29 and 30 may be mounted on levers 31 and 32 that ar-e pivotally supported by member Z also. The rolls 29 and Si) may comprise a plurality of individual disks 31A mounted on a shaft 32. The disks,V may have a cent-ral hole substantially larger than the diameter of shaft 32 so that eachhmayV move radially of `shaft 32 independently of each other.

The .weight of the assembly of disks 31 is such as to effectively compress the filter cake beneath the endless belt 23, so that the combined effectof the belt 23, rolls 29, and the dewatering vacuum to which the 'cake is subjected while above the slurry in tank 1t) ,provides a cake having a predetermined moisture content asfit Referring again to the drawing, a roll 33 is fixed toi I a shaftn33 that is journaledin bearings supported by a frame member 20. Referring to `FIG. 2, the drum 33 extends along an axis parallel to the axisof rotation of the drum 11, and extends` beyond the face width thereof.V AV plurality of resilient flapper sheets 34 may .be fixed to the roll 33, extending tangentially from its peripheral surface and located equidistant thereabout. These apper sheets 34 may extend through out the length of roll 33 and may be fastened thereto by screws 35 or other suitable means.

A pulley 56 may be fixed to the one end of shaft 33 and a belt 37 may connect it to a drive pulley 3S fixed to the output shaft of a motor 39 that may be'mounted on one of the uprights 19. E n v The roll 33 .is supported at a point ahead of the Acornpressing roll 3) and in the embodiment disclosed it is Y shown as being vertically above the axis-of rotation of drum 11. It is spaced from the periphery of drum 11 such that as the roll :53 is rotated, the flexible sheets V34 'slap against the belt 23 over its entire width and for a substantial lengthwise distance.

With a speed drum 11 within a range of about 3A to l0 revolutions per minute, and a speed of rotation of roll 33 within a range of about 60 to 150 revolutions per minute, a decrease in the moisture content of the filter cake over that produced without the compressing belt 23 and the flapper Vmeans 34 was in the order of about 40%. On the other hand, with thev compressing belt 23 andrliapper means -34 employed separately, the reduction in moisture content amounted to about 15% and 18%, respectively.

` Alternatively, the compressing device may comprise the rolls 29 and 30 independently of the belt 23, in which case, a flexible sheet 4t? having a width equal to the axialV lengthof the drum 11. may be supported from a bar 41 extending between the two curved frame members 20. The sheet 40 may lie beneath the roller 33 containing the fiappers 34.

Although the various features of the new ,and irnproved drum filter and dewatering means have been shown and described in detail to fully disclose one embodiment of the invention, it will be evident that'changes may be made in"such details and. certain features maybe used without others without departing from the principles of' the invention. Y

'What is claimed is: 'Y Y 1. In a drum filter, a'tank; a drum having a substantial portion thereof submerged within a slurry within said tank; a plurality of rolls spaced from the drum and parallel to the axis thereof, cake discharge means skurrounding a substantial portionof the periphery of said drum, tangentially leaving said drum, passing over said rolls and tangentially returning/to said drum; an end less compressing belt having a run'thereof Wrapped around a substantial arc ofthe periphery of said drum;` a plurality ofV compressing roll means acting at'spaced points along the run of said belt in contact with the periphery of said drum; a roll rotatableabout an axis parallel with the axis of rotationof said Vdrum and spaced'radially beyond theperiphery of said drum; exible members attached to said roll and extending radially outwardly -Whereby upon rotation of said roll said flexible members slap the run of said belt in-contact with the periphery of Asaid drum; and means for rotating Vsaidroll.

2. A filter according to claim l, wherein each of said flexible members comprises a continuous sheet.

References Cited in the file of this patent UNITED STATES PATENTS Great Britainy Mar. 2, 1955 

1. IN A DRUM FILTER, A TANK; A DRUM HAVING A SUBSTANTIAL PORTION THEREOF SUBMERGED WITHIN A SLURRY WITHIN SAID TANK; A PLURALITY OF ROLLS SPACED FROM THE DRUM AND PARALLEL TO THE AXIS THEREOF, CAKE DISCHARGE MEANS SURROUNDING A SUBSTANTIAL PORTION OF THE PERIPHERY OF SAID DRUM, TANGENTIALLY LEAVING SAID DRUM, PASSING OVER SAID ROLLS AND TANGENTIALLY RETURNING TO SAID DRUM; AN ENDLESS COMPRESSING BELT HAVING A RUN THEREOF WRAPPED AROUND A SUBSTANTIAL ARC OF THE PERIPHERY OF SAID DRUM; A PLURALITY OF COMPRESSING ROLL MEANS ACTING AT SPACED POINTS ALONG THE RUN OF SAID BELT IN CONTACT WITH THE PERIPHERY OF SAID DRUM; A ROLL ROTATABLY ABOUT AN AXIS PARALLEL WITH THE AXIS OF ROTATION OF SAID DRUM AND SPACED RADIALLY BEYOND THE PERIPHERY OF SAID DRUM; FLEXIBLE MEMBERS ATTACHED TO SAID ROLL AND EXTENDING RADIALLY OUTWARDLY WHEREBY UPON ROTATION OF SAID ROLL SAID FLEXIBLE MEMBERS SLAP THE RUN OF SAID BELT IN CONTACT WITH THE PERIPHERY OF SAID DRUM; AND MEANS FOR ROTATING SAID ROLL. 